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92d18d7fcd
* Rename Tag(s) to Event(s) - tag was replaced with event, but in some places it still mentions tag, would be easier to understand if we tried to replace it with event to not confuse people. Signed-off-by: Marko Baricevic <marbar3778@yahoo.com> * more changes from tag -> event * rename events to compositeKeys and keys * Apply suggestions from code review Co-Authored-By: Anton Kaliaev <anton.kalyaev@gmail.com> * add minor documentation on how composite keys are constructed * rename eventkey to compositekey Co-Authored-By: Anton Kaliaev <anton.kalyaev@gmail.com> * add changelog entry & add info to regenerate confid to changelog entry
90 lines
2.5 KiB
Go
90 lines
2.5 KiB
Go
package pubsub
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import (
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"errors"
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"sync"
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)
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var (
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// ErrUnsubscribed is returned by Err when a client unsubscribes.
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ErrUnsubscribed = errors.New("client unsubscribed")
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// ErrOutOfCapacity is returned by Err when a client is not pulling messages
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// fast enough. Note the client's subscription will be terminated.
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ErrOutOfCapacity = errors.New("client is not pulling messages fast enough")
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)
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// A Subscription represents a client subscription for a particular query and
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// consists of three things:
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// 1) channel onto which messages and events are published
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// 2) channel which is closed if a client is too slow or choose to unsubscribe
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// 3) err indicating the reason for (2)
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type Subscription struct {
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out chan Message
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cancelled chan struct{}
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mtx sync.RWMutex
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err error
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}
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// NewSubscription returns a new subscription with the given outCapacity.
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func NewSubscription(outCapacity int) *Subscription {
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return &Subscription{
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out: make(chan Message, outCapacity),
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cancelled: make(chan struct{}),
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}
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}
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// Out returns a channel onto which messages and events are published.
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// Unsubscribe/UnsubscribeAll does not close the channel to avoid clients from
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// receiving a nil message.
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func (s *Subscription) Out() <-chan Message {
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return s.out
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}
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// Cancelled returns a channel that's closed when the subscription is
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// terminated and supposed to be used in a select statement.
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func (s *Subscription) Cancelled() <-chan struct{} {
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return s.cancelled
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}
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// Err returns nil if the channel returned by Cancelled is not yet closed.
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// If the channel is closed, Err returns a non-nil error explaining why:
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// - ErrUnsubscribed if the subscriber choose to unsubscribe,
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// - ErrOutOfCapacity if the subscriber is not pulling messages fast enough
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// and the channel returned by Out became full,
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// After Err returns a non-nil error, successive calls to Err return the same
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// error.
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func (s *Subscription) Err() error {
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s.mtx.RLock()
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defer s.mtx.RUnlock()
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return s.err
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}
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func (s *Subscription) cancel(err error) {
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s.mtx.Lock()
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s.err = err
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s.mtx.Unlock()
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close(s.cancelled)
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}
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// Message glues data and events together.
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type Message struct {
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data interface{}
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events map[string][]string
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}
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func NewMessage(data interface{}, events map[string][]string) Message {
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return Message{data, events}
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}
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// Data returns an original data published.
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func (msg Message) Data() interface{} {
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return msg.data
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}
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// Events returns events, which matched the client's query.
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func (msg Message) Events() map[string][]string {
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return msg.events
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}
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